Igniter



Nov. 2, 1965 R. L. HARGETT 3,214,910

IGNITER Filed Feb. 18, 1964 2 Sheets-Sheet 1 FIG.1

Richard L. Hargett INVENTOR.

BY ATTORNEY AGENT.

Nov. 2, 1965 HARGETT 3,214,910

IGNITER Filed Feb. 18, 1964 2 Sheets-Sheet 2 FIG. 3

Richard L. Hargefl INVENTOR.

BY ATTORNEY.

AGENT United States Patent 3,214,910 IGNITER Richard L. Hargett, Frederick, Md., assignor to the United States of America as represented by the Secretary of the Navy Filed Feb. 18, 1964, Ser. No. 345,810 Claims. (Cl. 60-39.82)

(Granted under Title 35, US. Code (1952), see. 266) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

This invention relates generally to igniters of the type used for starting rocket motors. In one of its more specific aspects the invention relates to an ignition means for igniting bodies of solid propellant supported within rocket housings. More particularly, it relates to an improved safety and arming mechanism for an igniter of the type described.

In rockets or missiles of the type described, the propellant is generally ignited by an ignition or booster charge positioned in the end of the rocket housing, and provided with an electrically controlled squib igniting means mounted at its outer end, external to said housing. A design criteria of such igniting means requires the provision of a safety mechanism capable of preventing premature ignition of the booster charge. Previous methods, which used mechanical as well as electrical safeties, employed housings built to physically contain the energy of the squibs. The monitoring and an out-of-line control of the squibs and booster and a shutter positioned therebetween was accomplished by use of a gear train operated cam and switch arrangement. Great care had to be taken, however, in the assembly of such units or they would not be safe. Moreover, in storage and in shipping, slippage of the elements often ruined the outof-line control so that a safe indication would be given when the mechanim was in fact armed for firing.

The present invention avoids the shortcomings and overcomes the accompanying difficulties encountered by igniters of this type in the past, and provides a safe and reliable means for starting a rocket motor. In a preferred form of construction, the disk type igniter of the present invention consists of three major parts including a support body which is affixed to the rocket motor, a disk or shutter having gear teeth out in a portion of it circumference and a printed circuit secured to its outer su face, and a block containing a pair of igniter squibs, a setting motor, and electrical connections, including the brushes that contact the printed circuit, for driving the motor and thereby rotating the disk. The block is aligned on a hub of the support body by a key so as to place the squibs contained therein in alignment over two openings in the support body leading to the booster on the opposite side thereof, but the squibs are maintained completely isolated from the rocket motor until the disk, positioned intermediate the block and the support body and having a pair of apertures therein, is rotated into the firing position to provide an igniting path for the igniter.

According to the present invention, it makes no difference in what position the disk is located in assembly.

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One simply has to push the unarm or safe button, and the disk is rotated to the safe position where it stops automatically. Unlike other systems, the disk or shutter cannot get out of step with the switches because the printed circuit that is permanently secured thereto controls the positioning or setter motor.

As a further safety measure, instead of trying to contain an explosive charge, should the squibs fire by accident while the igniter is in the safe position, the shutter of the present invention is designed to simply deflect the energy into a safe expansion volume, whereby it is rendered harmless.

It is accordingly an object of the present invention to provide a new and improved igniter for starting rocket motors that is both safe and dependable.

Another object of the present invention is to provide a new and improved safety and arming mechanism for an igniter of the type used in starting rocket motors.

Still another object of this invention is to provide an igniter of the type described having an improved safety mechanism in which the control circuit therefor is an integral part of the safety mechanism.

Other objects, advantages and novel features of the invention will become apparent from the following de tailed description of the invention when considered in conjunction with the accompanying drawings, wherein:

FIG. 1 is a sectional view through the housing of an igniter constructed according to the present invention;

FIG. 2 is a section taken along line 2-2 of FIG. 1; and

FIG. 3 is a section taken along line 33 of FIG. 1.

Referring now to the drawings wherein like reference numerals have been used to designate like parts, and initially to FIG. 1, there is illustrated a support structure generally indicated by the numeral 10 and adapted to be bolted to a rocket motor (not shown) as indicated at 11. Obviously, the support structure might be fixed to the rocket motorby some other means such as, for example, through a threaded connection. When affixed to the rocket motor, the support structure 10 is designed to threadably receive a booster or ignition charge (not shown), positioned in the rear end of the rocket housing, within end wall 12 in threaded portion 13 thereof. End wall 12 of the support structure 10 is further provided with a pair of through openings 14 leading to the igniter chamber 15 and providing a passage for the energy released therein to the booster charge of the rocket motor.

Within the igniter chamber 15 there is a block member 16 positioned on a hub portion 17 extending laterally from the end wall 12 of the support structure 10, and aligned thereon by a key protrusion 18 slidably mounted in a slot 19 in the hub 17. The block 16 carries two igniter squibs 21 which are automatically maintained in aligned relationship with openings 14 in end wall 12 by the keyed connection heretofore described of the block 16 to the hub portion 17.

Between the block 16 and end wall 12 there is rotatably mounted on the hub '17 a disk or shutter member 22 having a pair of apertures 23 therein, which provide an i=gniting path to allow the squib energy to pass to the motor chamber when the disk is in firing position. When the disk is rotated, however, to the unarmed position in which the apertures 23 are not aligned with the squibs .2 1 and openings 14 in wall l -2, the disk blocks the ignition path to prevent passage of the squib energy to the motor chamber. Disk $2 is provided with gear teeth 24 cut into a portion of its circumference, and is further provided with a plastic laminate circuit board 25 secured to a portion of its surface adjacent block 16 diametrically opposite that portion having .gear teeth therein. The board 25 has circuitry printed thereon in the form of two arcu'ate conductive strips 26 and '27, one being of less than onehalf the length of the other and located radially inside of and adjacent one end of the other on the disk 22.

Within the block 16 there is a plurality of through passages threaded at the end adjacent the disk 22 for receiving in threaded engagement plastic housings 28 containing copper brushes Z9 that contact the strips 26 and Q17. These brushes are so arranged in the block as to form a control circuit, acting through a motor 31 and a gear reduction network 32 engaging the gear teeth 24 on disk Q2, as shown best in FIG. 2, upon application of potential to cause rotation of disk $2 in one direction, and upon reversal of the polarity to rotate disk 22 in the --other direction. In each case, when the disk has been rotated sufficiently so that the conductive strips are removed from contact with a given set of brushes and placed in contact with another set, the disk stops automatically. For example, in the position best illustrated in FIG. 3, strip 26 represents a closed switch making contact with brushes A and B, whereas strip 27 represents a closed switch making contact between brushes -D and E. On the other hand, if disk 22 were rotated counterclockwise (as viewed in FIG. 3), strip 26 then would make contact between brushes L and M, whereas strip '27 would make contact between brushes E and F. In the positions at the extremes of rotation in each direction, the 'disk is first in the unarmed position and then in the aligned or firing position. In this manner, the switch circuitry controlling the positioning motor 31 is secured permanently to the disk or shutter 22, and therefore the disk cannot get out of step with the switches. Connections to the exterior of the igniter chamber I are effected through the connector assembly 33, which is adapted to be keyed with a sealing connector sleeve housing (not shown) to be received in passage 34 of body '10.

Another safety feature of this invention is found in the manner of installation of the disk 22, precisely in providing it with slightly more space than required on the hub portion 1 so that the disk may yield to the force of an accidental firing of the squibs, rather than try to contain it. Since this hot gas may then expand in the igniter chamber or expansion chamber 15, where the heat will be absorbed by the metal support structure 10, the efiect is to render such an accidental firing completely harmless. By merely replacing the fired squib, the igniter device may be quickly readied for operation again.

Obviously many modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. An igniter device for starting a rocket motor comprising,

'a housing means connected to the rocket motor,

at least one electroresponsive detonator mounted within said housing means,

said housing means having a pair of apertures in the end wall thereof connected to said rocket motor for allowing the hot gases of the detonator to pass to an ignition charge in the rocket motor,

a hub extending from said end wall into said housing means,

shutter means mounted within said housing on said hub between said detonator and said housing apertures and having a pair of through passages normally i out of line with said housing apertures in the unarmed position, said shutter means being slightly spaced from the end wall and capable of axial movement along the hub in said space upon accidental detonation of one of the electroresponsive detonators,

and motor means within said housing for rotating said shutter means from the unarmed position to the armed position by rotating the through-passages in said shutter means until they are aligned with the apertures in said housing means,

whereby said detonator is ignited and the hot gases pass through the openings in said shutter means and said housing means to ignite the ignition charge in the rocket motor.

'2. An igniter device for starting a rocket motor \comprising,

a housing means connected to the rocket motor and having at least one aperture in the end wall thereof connected to said rocket motor,

a support block fixedly mounted within said housing means,

electroresponsive detonator means positioned in said block and aligned with said housing aperture for allowing thehot gases of the detonator to pass to an ignition charge in the rocket motor,

shutter means rotatably mounted within said housing means between said support block and said end wall of said housing means and having at least one passage therethrough normally out of line with said housing aperture in the unarmed position.

motor means Within said housing for rotating said shutter means from the unarmed position to the armed position by rotating the passage in said shutter means until it is aligned with the aperture with the aperture in said housing end wall,

and motor control means including a printed circuit on said shutter means and cooperating brushes positioned in said support block,

whereby when said motor is actuated to rotate said shutter means, the shutter will positively stop in the desired position.

3. An igniter device according to claim 2 wherein said shutter means is a disk.

4. An igniter device for starting a rocket motor comprising,

a housing means connected to the rocket motor and having a plurality of apertures in the end wall thereof connected to said rocket motor,

a hub portion extending from said end wall into said housing means, said hub portion having a slot therein,

a support block fixedly mounted within said housing means on said hub portion and having a key projection slideably fitted into said slot,

a plurality of electroresponsive detonators positioned in said block and aligned with said apertures in the end wall of said housing for allowing the hot gases of the detonators to pass to a booster change in the rocket motor on the opposite side of said end wall,

disk means rotatably mounted within said housing means on said hub portion between said support block and said end wall of said housing means and having a plurality of passages therethrough normally out of line with said housing apertures in the unarmed position, said disk means being slightly spaced from the end wall and capable of axial movement along the hub in said space upon accidental detonation of one of the electroresponsive detonators,

said disk having gear teeth out into a portion of its circumference and printed circuit means secured to its surface adjacent said support block,

motor means within said housing cooperating with said gear teeth for rotating said disk means,

and motor control means including brushes positioned 5 in said support block that contact said printed circuit means,

whereby said motor may be actuated to rotate said disk means in one direction to the unarmed position and in the other direction to the firing position.

5. An igniter device according to claim 4 wherein said printed circuit means includes a pair of arcuate conductive strips, one being of less than one-half the length of the other and positioned radially inside of the other on the disk surface.

6 References Cited by the Examiner UNITED STATES PATENTS MARK NEWMAN, Primary Examiner.

RALPH D. BLAK'ESLEE, Examiner. 

1. AN IGNITER DEVICE FOR STARTING A ROCKET MOTOR COMPRISING, A HOUSING MEANS CONNECTED TO THE ROCKET MOTOR, AT LEAST ONE ELECTRORESPONSIVE DETONATOR MOUNTED WITHIN SAID HOUSING MEANS, SAID HOUSING MEANS HAVING A PAIR OF APERTURES IN THE END WALL THEREOF CONNECTED TO SAID ROCKET MOTOR FOR ALLOWING THE HOT GASES OF THE DETONATOR TO PASS TO AN IGNITION CHARGE IN THE ROCKET MOTOR, A HUB EXTENDING FROM SAID END WALL INTO SAID HOUSING MEANS, SHUTTER MEANS MOUNTED WITHIN SAID HOUSING ON SAID HUB BETWEEN SAID DETONATOR AND SAID HOUSING APERTURES AND HAVING A PAIR OF THROUGH-PASSAGES NORMALLY 